Heating apparatus



July 4, 95() E, BMLEY 51@ au? lagd HEATING APPARATUS Filed Feb. 6, 1948 I? il: E 1 4:

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Patented July 4, 195,0

HEATING APPARATUS Edgar L. Bailey, Birmingham, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware UNITED STATES PATENT OFFICE Application February 6, 1948, Serial No. 6,644

(Cl. 21S-38) 11 Claims. 1

My invention relates to heating apparatus and more particularly to apparatus of the electrically energized and controlled type for heating liquid.

One of the principal objects of my invention is to provide heating apparatus of the type which is readily adaptable to heat water for domestic and commercial use.

Another object of my invention is to provide heating apparatus with electrically controlled heating means for gradually applying heat to the liquid.

A further object of my invention is to provide heating apparatus having inherent control features thereby eliminating the need of all thermostats, switches, and the like.

Still another object of my invention is to provide heating apparatus which will demand a small amount of electrical power for use over a long period of time instead of a large amount of power over a short periody of time thereby eliminating overloading of the power supply circuit.

Other objects and advantages of my invention will become more apparent from the followy:ing description taken in conjunction with the accompanying drawings in which:

Fig. l is side elevational view of heating appa- :ratus embodying my invention.

Fig. 2 is a vertical sectional View taken on line 2 2 of Fig. l of the heating element used in .my improved heating apparatus.

Fig. 3 isa transverse sectional View taken on 'the line 3-3 of Fig. 2.

Fig. 4 is a schematic View of the electric circuit 'shown in Figs. 1 and 2.

Fig. 5 is a side elevational view partly in section showing a modified form of my invention.

Fig. 6 is a fragmentary, enlarged, vertical sectional view of the heating unit embodied in the form of the invention illustrated in Fig. 5.

Referring now to Figs. 1, 2, 3 and 4, I have shownfa conventional heating tank I having a liquid inlet Il and an outlet I2 for, respectively receiving liquid to be heated and dispersing same after it has been heated. The tank I0 is also provided with ports I3 and I6 for receiving one extremity of pipes I and I6, respectively. The other extremity of the pipes I5 and I6 are threaded to be received in T-fittings I'l and I8, respectively. The fitting Il has a pipe I9 threaded into one extremity of its T-structure, while the other extremity of the T-structure is provided with a plug threaded therein. The pipe I9 extends upwardly from the T-tting Il' to be received in the lower extremity of a heating unit generally designated by the numeral 2I.

The tting I8 is similarly provided with a pipe 22 threaded in one extremity of its T-structure and is similarly provided at its other extremity with a threaded plug 23. The pipe 22 extends down- Wardly from the iitting I3 to be received in the upper extremity of the heating unit 2|. The plugs 20 and 23 may be removed to facilitate cleaning of the entire heating unit.

The heating unit ZI comprises a heat transfer tube 24 which is positioned between and securely tted to the adjoining extremities of the pipes IS and 22 and is provided with threaded ends 25 and 26 which have collars 2l and 28, respectively, threaded thereon. The adjoining extremities of pipes I9 and 22 are similarly threaded to be received within the threaded collars 28 and 2l, respectively. A coil 28 is wound around the tube 24 and is separated from the tube by an elongated cylindrical insulator 29. The entire heating unit is enclosed within a cylindrical casing 3B which is similarly separated from the coil 23 by a cylindrical insulator 3|. The casing 30 has disposed therein a pair of passages 32 and 33 for receiving the electrical connections of the coil 28. The passage 3l accommodates a wire 34 which connects one extremity of the coil 28 to one contact 35 of a capacitor 36. The other` contact 3l of the capacitor is connected by a wire 38 with an electrical source (not shown). The passage 33 accommodates a wire 3S which is connected to the other extremity of the coil 28 and to the electrical source (not shown) The magnetic characteristics of the metal of the heat transfer tube 24 are such that its permeability varies inversely with temperature changes. Certain alloys oi metals such as nickel and iron have these characteristics and at certain temperatures known as their Curie points they become ineffective to pass significant magnetic flux. By selecting the proper alloy composition and proportions of alloy constituents, it is possible to predetermine quite accurately the maximum temperature to which material or liquid may be heated. For example in heating water in accordance with the invention, an alloy comprising approximately about 39% nickel and 61% iron is desirable for this alloy has a Curie point of about C. This alloy is commercially known as Carpenter Temperature Compensator No. 30. Various other alloys may be employed depending upon the Curie temperature desired.

The tube 24 acts as a core for the coil 28 and therefore its variation in permeability due to temperature change regulates the inductance of the coil. When an alternating electric current is applied to the coil 28 an amount of heat is dissipated therefrom which is dependent upon the circuit characteristis. This heat is transferred to the core 24 thereby creating a heat transfer surface across which the liquid to be heated passes. When the tank I is iilled with liquid the passage formed by the pipe I5, the T-i'ltting I1, the pipe I8, the tube 24, the pipe 22, the fitting I8 and the pipe I6 is also filled with liquid. It may also be readily seen when Viewing Fig. 1, that when the level of the liquid in the tank II) is substantially above the halfway mark of the tank, there will be liquid within the tube 24. As the liquid within the tube 24 is heated, it rises and enters the tank through the port I4 and more relatively cool liquid is supplied to the tube 24 from the port I3. In this way the entire liquid content of the tank II) is heated.

Referring now more particularly to Fig. 4, I have shown a wire diagram of the circuit shown in Figs. 1 and 2. The diagrammatic illustrations of the resistor 48 and inductance 4I appearing in Fig. 4 represent electrically the inherent resistance and the electrical inductance of the coil 28, respectively. The capacitor 42 is the electrical equivalent of the capacitor 36 shown in Figs. 1 and 2. It can be readily seen that the coil and thecapacitor are electrically in series. When the core 24 is at a predetermined low temperature, forr example when the liquid to be heated has just entered the tank E3, the reactance of the coil is equal to the predetermined reactance of the capacitor. Therefore, since the coil and the capacitor .are in series `and the two are electrically 180 out of phase in an alternating current circuit, these reactances cancel each other and the only resistance in the circuit is that which is inherent within thecoil 28. As a result, a predetermined relatively high .amount of current flows in the circuit. This causes a relatively high voltage drop across the coil and consequently the maximum heating of the coil is reached under these conditions.

As heretofore described, when the coil 28 supplies heat to the heat transfer tube 24 and thus to the liquid within the tube, the temperature of the tube gradually rises which causes the permeability to gradually decrease. Under these conditions, the ability of the tube 24 to conduct magnetic flux therethrough similarly decreases and the inductive reactance of the coil is not great enough to counterbalance the capacitive reactance of the capacitor 3B. Therefore, the overall resistance of the circuit is now determined not only by the inherent resistance of the coil 28, but also by that portion of capacitive reactance which is not counterbalanced by the reactance of the coil. Since now there is more impedance within the circuit, the current is less, the voltage drop across the coil is correspondingly less and the heat supplied by the coil is less.

As the temperature of the core 24 gradually approaches a predetermined high temperature, more and more impedance is added to the circuit since more .and more of the capacitive reactance of the capacitor is not counterbalanced by the reactance of the coil. When this predetermined high temperature is reached by the core 24, which is commonly referred to as its Curie point, the core 24 is no longer able to pass lmagnetic iiux. Therefore, the inductive reactance of the coil 28 is very small compared to the capacitive reactance of the capacitor 36 and the resulting very high which are adapted to receive and deliver liquid to 52 also decreases as the temperature rises.

be heated to and from the tank. A heating unit generally designated by the numeral 46 is positioned within the tank 43 and is enclosed within a casing 41 which is secured to the inner wall of the tank 43, and filled With heat conducting medium such as oil.

The unit 46 comprises a transformer core 49 secured to the inner wall of tank 43' by a pair of brackets 58 and having a primary coil 5I and a secondary coil 52 Wound thereon. The primary coil 5I is provided with leads 53 which extend through the opening 54 in the tank 43 and are connected to an electrical source of A. C.current (not shown). The combination of the coil 5 l, the leads 56 and the source comprise a primary circuit.

The secondary coil 52 is provided with leads 55 whichextend through the opening 56 in the tank 43 and are connected to a capacitor 51 so that the coil 52 and the capacitor 51 are electrically in series. The combination of the coil 52, the leads 55 and the capacitor 51 form a secondary circuit. The openings 54 and 56 through which the leads 53 and 55 extend are sealed in a conventional manner not shown to prevent the escapement of the contents of the casing 41. That portion of the core 48 designated by the nu-meral 58 on which the coil 52 is wound and the coil 52 comprise the heat transfer surfaces of the unit. The portion 58 is electrically connected to the rest of the core 49 and may be made of the same material as used in the structure shown in Figs. 1 through 4 such as a nickel alloy.

When current ows in the primary circuit, the coil 5I causes the low of magnetic flux through the core 49 and portion 53 thereby inducing a voltage across the coil 52 which in turn causes current to flow in the secondary circuit. It can be readily seen that the core portion 58 acts as a core for the coil 52 and thereby regulates both the inductance and the inductive reactance of the coil 52. The properties of the core portion 58 are such that as its temperature rises, its ability to pass magnetic flux decreases. As a result the inductance and inductive reactance of the coil This rise in temperature is caused by the heat dissipated by the coil 52, dueto its inherent resistance when current flows in the secondary circuit.

The value of the capacitor 51 is predetermined so its reactance to equal the reactance of the coil 52 when the temperature of the core portion 58 is at a relatively low value such as when liquid to be heated rst enters the tank. Since the reactances of a coil and a capacitor in series are out of phase and since the reactances of the coil 52 and the capacitor 51 are equal at the aforementioned low temperature the reactances cancel each other and the only resistance left within the secondary circuit is that which is inherent Within the coil 52. As a result a large amount of current flows in the secondary circuit due to the low amount of impedance therein and a large amount of heat is dissipated from the coil 52. This heat is transferred to the core portion 58 due to the close proximityiof thefcoi'l 52 'theretofand .hence to the liquid to beheated through :the .heat yconducting mediumgand thecasing 4?'.

.As the temperature ofthe coreportion 58 .-rises, it losesthe ability toipass .magnetic flux thereby reducing the inductive reactance cf thevcoil 52. As a result the capacitive'rea'ctance'of the aca.- pacitor l5'! is not counterbalanced by the -`reactance of the coil 52 and additional impedance abe., sides that which is inherent within .the coil 52 is added to the secondary circuit.

With additional impedance in the secondary circuit, the current therein .is accordingly re.- duced which in turn reduces; the heat dissipated by coil 52. The inductive reactance 'of the coil 52 continues to decrease untila predetermined high temperaturey is reached. .Atl this temperature, which is vcommon-ly referred toi as the Curie pointof the core portion V58, the portion 58 is vno longer able to ,passmagnetic flux, the reactance of the coil 52 `is very low.,` the current in the secondary 4circuit is very low since the 4impedance in the circuit is very high, and the coil 52 is unable to dissipate enough heat .to heat .the liquid .in the tank 43 further. The temperature of the liquid at this point is lat :a predetermined Value.

However, when lthe temperature of the liquid in the tank 43 is reduced, .such as when fresh liquid to be heated enters the tank, the temperature of the core `portion is accordingly reduced since this temperature reduction is communicated `to the core portion k5.8 through the casing 41 and the heat conducting medium therein.

Under these conditions, magnetic .Ilux again passes through the core 4portion '58.the impedance of the secondary circuit is reduced and :a greater current again flows, the coil 52 dissipates heat, and the vliquid in the tank 43 is onceaga-in heated until the Curie .point rof 'the core portion 58 is reached.

It should be noted that both v:Ecrins of heating apparatus disclosed herein vthe current required is varied gradually at `all times. .It may be easily seen that the temperatures of the core portions and the liquid to be heated rise or .fall gradually. vAs a result when this .apparatus is employed no instantaneous roverloads fof the power circuit supplying. electrical current `to .the apparatus is involved.

Although but several embodiments 'of 'the invention `are herein shown and described, it will be understood that various .changes in the details of construction .andmaterials employedmay be made `without departingirom .the :spirit of the invention.

Iclaim:

y1. Heating 'apparatus comprising a container for material tobe heated, a heat transfer surface associated with said container icomprisinga mag.- netic flux core portion having temperature sensitive permeability, the permeability of said core portion decreasing upon temperature riseto :a substantially ineffective value'at a predetermined desired temperature, and :an electrical system including a combined resistance heating element and ux yproducing means for impressing a .flux in and heating saidcorezportion and a capacitor having a capacity predetermined to form a tuned and detuned circuit with said meanswhen said core portion is at desired predetermined lowland.

high temperaturesrespectively.

2. Heating .apparatus comprising .a container for .material to `be heated, -a heat Vtransfer surf-ace associated with .said container .comprising .a mag-l :netic flux core portionv having temperature lsensh tive permeability, athepermeability of .said lcore portion decreasing upon ltemperature rise and :nally becoming ineiective .to pass magnetic Vflux when a predetermined high temperature is reached, :an electrical system including means Afor impressing .a iiux in said core portion, said means having an inherent electr-ical resistance for dissipating maximum heat to said core portion and said .material under predetermined conditions 4of current flow in said system, and a capacitor in 4said system having -a capacity predetermined to form a `tuned circuit with said means when said core portion .is at a predetermined .low temperature, said circuit departing gradually from said tuned condition as said permeability decreases in .response to temperature rise .thereby reducing -thefiow of current in said system gradually until said high temperature is reached at which time said resistance is ineffective to further heat said material.

'3. Heating .apparatus comprising a container vfor .material to be heated, a heat transfer surface associated Withsaid container comprising a magu netic flux core having a temperature sensitive permeability, the permeability of said `core Idecreasing upon temperature rise and finally becoming substantially ineffective to pass magnetic iiux when a predetermined high temperature is reached, a circuit including means for impressing a Vilux in said core, said means having an inherent electric resistance for dissipating maximum heat to said core and said material when `a pre-- determined current iiows in said circuit, and a capacitor in said circuit having a capacity predetermined to cooperate with said means for tuning said circuit when said core is at a predetermined low temperature, said circuit departing gradually from said tuned condition as said permeability decreased in response to temperature rise there by reducing the .flow of said current in said circuit gradually until vsaid high temperature is reached Yat which time said resistance is ineffec-` tive to further heat said material.

4. Apparatus for heating liquid comprising a heat transfersur-face having `a magnetic flux core in the form of a tube vfor accommodating .the flow of liquids therethrough, said core comprising metal having a temperature sensitive 'permeability whichldecreases upon temperature rise and nally becomes ineffective to pass flux when a predetermined high temperature is reached, an electrical circuit including an inductive coil `positioned around said core and .adapted to impress a flux therein, said coil having an inherent electrical resistance which facilitates the supply :of maximum heat to said core and said liquid when a predetermined .current flows in said circuit, and -a capacitor in series with said .coil yin said circuit having a capacity predetermined to form-a tuned circuit with said coil when saidv core is at a predetermined -low temperature, said circuit departL ing gradually from said tuned condition as said permeability decreases in response to temperature rise thereby reducing the flow of :said current rin said circuit gradually until said high temperature is reached at which time said .coil is ineffective to further. heat said liquid.

5. Heating apparatus comprising a container for lmaterial to be heated, a heat transfer sur@ face in said container comprising a magnetic liux .core lportion .having temperature sensitive permeability, the ,permeability of said core porn tion decreasing vupon temperature rise and iinally becoming ineffective .to pass .magnetic iiux when .a predetermined high temperature is reached, an

electrical system including a source of electricity, first means for impressing a ux in saidI core portion, second means for impressing a ux insaid core portion, said second means being inductively coupled to said first means and having an inherent electrical resistance which facilitates the supply of maximum heat to said core portion and said material when a predetermined current ows therethrough, and a capacitor in said system having a capacity .predetermined to form a tuned circuit withl said second means vwhen said core portion is at a predetermined low temperature, said circuit departing gradually from .said tuned condition as said permeability decreases in response to temperature rise thereby reducing the flow of said current through said second means gradually until said high temperatureis reached at which time said resistance is ineifec tive to further heat said material.

6. Apparatus for heating Water comprising a tank, inlet and outlet ports in said tank for receiving Water to be heated and discharging heated water, respectively, -a container within said tank and sealed therein from said water, heat conducting medium Within said container, a metal core member positioned within said container having a portion thereof provided with magnetic characteristics such that the permeability of said portion decreases lon temperature rise and becomes ineiective to pass magnetic iux at a .predetermined desired temperature, and an electrical system including a primary coil positioned around said core member for impressing a flux therein, a secondary coil positioned around said core portion and inductively coupled to said primary coil, said primary and secondary coils having an inherent electrical resistance for dissipating maximum heat to said core portion and said medium under .predetermined conditions of current flux, and a capacitor having a capacity predetermined to form a tuned circuit with said secondary coil when said core portion is at a predetermined low temperature. y

7. Heating` apparatus comprising' a container for material to be heated, a heattransfer surface 'associa-ted with said container including a magnetic flux core portion comprising a nickel alloy having temperature sensitive permeability, the permeability of said core portion decreasing upon temperature rise and finally becoming inelective to pass magnetic ux when -a predetermined high temperature is reached, an electrical system including means for impressing a flux in said core portion, said means having an inherent electrical resistance for dissipating maximum heat to said core portion and said material under-predetermined conditions of current flow in said system, and a capacitor in said system having la capacity predetermined to form a tuned circuit with said means when said core portion is at a predetermined low temperature, said circuit departing gradually from said tuned condition as said permeability decreases in response to temperature rise thereby reducing the flow of current in said system gradually until said high temperature is reached at which time said resistance is ineiective to further heat said material.

8. Heating apparatus comprising a container for material to be heated, a heat transfer surface associated with said container including amagnetic flux core comprising a nickel alloy 'having a temperature sensitive permeability, the permeability of said core decreasing upon temperature rise and finally becoming substantially ineiectivc lto pass magnetic flux when a predetermined high temperature is reached, a circuit including means for impressing a ux in said core, said means having an inherent electric resistance for dissipatingv-maximum heat to said core and said material When a predetermined current flows in said circuit, anda capacitor inY said circuit having a capacitypredetermined to cooperate with said means for tuning saidcircuit when said core is at a p'redeterminedlow temperature, said circuit departing gradually fromsaid tuned condition as said permeability decreases in response to temperature rise'thereby reducing the iloW of said current iinv said circuit gradually until said high temperature 'is reached at which time said resistance is ineffective to further heat said material.

9. Apparatus -for heating liquid comprising a heat transfer surface having va magnetic flux core comprising a nickel alloy in the form of a tube for accommodating the flow of liquids therethrough, said core comprising metal having a temperature sensitive permeability which decreases upon temperature rise and nally becomes ineiective `to pass ilux when a predetermined high temperature is reached, an electrical circuit includingan inductive coil positioned around said core and adapted to impress a iiux therein, Isaid coil having an inherent electrical resistance which facilitates the supply of maximum heat to said core and said liquid when a predetermined current flows in said circuit, and a capacitorvin series vvithv said coil in said circuit having-a capacity predetermined to form a tuned vcircuit'vvith said coil when said core is at a predetermined low temperature, said circuit departing-gradually from said tuned condition as said permeability decreases in response to temperaturerise thereby reducing the iiow of said current in said circuitgradually until said high temperature is reached at which time said coil is ineiective to further heat said liquid.

10. Heating apparatus comprising a container for material to be heated, a heat transfer surface in said container comprising a magnetic flux core portion comprising a nickel Aalloy having temperature sensitivepermeability, the permeability of said'fcore portion decreasing upon temperature rise and finally becoming inefective to pass magnetix vflux when'a predetermined high temperature is reached, an electrical system including a source of electricity, rst means -for impressing a flux in saidicore portion, second means for im- .pressing al flux. in said core portion said second means being inductively coupled to said rst means and having an inherent electrical resistance Which facilitates the supply of maximum heat to said core portion and said material when a predeterminedcurrent nows therethrough and a capacitor invsaidsystem having a capacity predetermined to` form a -tuned circuit with said second meanswhen said core Vportion lis at a predetermined low temperature, said circuit departing gradually from said tuned -condition as said permeability -decreasesin response to temperature rise therbyr'educing the-flow of said current through said'secondmeans gradually until said high temperature is reached at which time said resistance isy ineiTecti've-to' yfurther heat said material.

11. Heating vapparatus comprising a container for material to'be heated, a heat transfer surface associated with said container comprising a magnetic flux core portion comprising approximately about 39 percent nickel and 61 per cent iron having vtemperature sensitive permeability, the per-vy meability of said core portion decreasing upon temperature rise and finally becoming ineffective to pass magnetic ux when a .predetermined high temperature is reached, an electrical system including means for impressing a flux in said core portion, said means having an inherent electrical resistance for dissipating maximum heat to said core portion and said material under predetermined conditions of current ow in said system, and a capacitor in said system having a capacity predetermined to form a tuned circuit with said means When said core portion is at approximately 65 F. temperature, said circuit departing gradually from said tuned condition as said permeability decreases in response to temperature rise thereby reducing the ow of current in 10 said system gradually until said high temperature is reached at which time said resistance is ineffective to further heat said material.

EDGAR L. BAILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,260,564 Magnusson et al. Mar. 26, 1918 1,750,640 Kitteredge et al. Mar. 18, 1930 1,981,632 Northrup Nov. 20, 1934 1,990,238 McDonald Feb. 5, 1935 2,265,470 Black Dec. 9, 1941 

